Ratios of Surface Area to Volume For Common Fine Fuels

The ratio of surface area to volume (σ), an indicator of fuel flammability, was determined for needles of eight conifer species, five grasses, leaves of two hardwood species, and a beard lichen. Surface area and volume of needles, grasses, and lichens were estimated, using measurements of perimeter, cross-sectional area, and length; similar estimates for hardwood leaves were made, using blueprint outlines and thickness. Calculations of σ from these estimates gave values ranging from 45 cm²/cm³ to 632 cm²/cm³. Shape factors, relating measured cross-sectional perimeters to circumferences calculated from measured cross-sectional areas as circles, ranged from 1.1 to 4.3. Minor errors in σ are traceable to several sources in the method, but accuracy is hard to assess because true surface is difficult to define. Forest Sci. 16:101-105.